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At least 19 recordsLinked to original sources
PubMed2024

Oceanic islands act as drivers for the genetic diversity of marine species: Cardita calyculata (Linnaeus, 1758) in the NE Atlantic as a case-study.

Geographic distribution, as well as evolutionary and biogeographic processes and patterns of marine invertebrate benthic species are strongly shaped by dispersal ability during the life cycle. Remote oceanic islands lie at the brink of complex biotic and abiotic interactions which have significantly influenced the biodiversity patterns we see today. The interaction between geological environmental change and taxon-specific dispersal modes can influence species evolutionary patterns, eventually delimiting species-specific biogeographic regions. In this study, we compare the population genetic patterns of the marine bivalve Cardita calyculata in the northeast Atlantic, discussing the role of Macaronesian islands during past climatic cycles. The genetic structure and diversity patterns were outlined based on SSR-GBAS loci of 165 individuals and on the mitochondrial COI marker of 22 individuals from the Canary Islands, Madeira, Azores and the Mediterranean. The highly structured genetic pattern found among regions and within archipelagos suggests the central role of oceanic islands in promoting the divergence of the species in both the NE Atlantic and the Mediterranean. The high degree of divergence in the COI dataset (> 7%) suggests the existence of potential cryptic speciation that needs to be further explored with a more comprehensive sampling. Such patterns are only congruent with a scenario where C. calyculata populations were maintained during glacial/interglacial cycles, supporting the role of the studied archipelagos as drivers of diversity for marine biota. We stress the importance of developing studies for species with various life history and dispersal modes. In such a way, a more profound understanding of the biogeographic and evolutionary significance of oceanic islands can catalyse directed conservation efforts, especially in the context of the ongoing climate crisis.

Animals↗
PubMed2024

Repeated evolution on oceanic islands: comparative genomics reveals species-specific processes in birds.

Understanding the interplay between genetic drift, natural selection, gene flow, and demographic history in driving phenotypic and genomic differentiation of insular populations can help us gain insight into the speciation process. Comparing patterns across different insular taxa subjected to similar selective pressures upon colonizing oceanic islands provides the opportunity to study repeated evolution and identify shared patterns in their genomic landscapes of differentiation. We selected four species of passerine birds (Common Chaffinch Fringilla coelebs/canariensis, Red-billed Chough Pyrrhocorax pyrrhocorax, House Finch  Haemorhous mexicanus and Dark-eyed/island Junco Junco hyemalis/insularis) that have both mainland and insular populations. Changes in body size between island and mainland populations were consistent with the island rule. For each species, we sequenced whole genomes from mainland and insular individuals to infer their demographic history, characterize their genomic differentiation, and identify the factors shaping them. We estimated the relative (Fst) and absolute (dxy) differentiation, nucleotide diversity (π), Tajima's D, gene density and recombination rate. We also searched for selective sweeps and chromosomal inversions along the genome. All species shared a marked reduction in effective population size (Ne) upon island colonization. We found diverse patterns of differentiated genomic regions relative to the genome average in all four species, suggesting the role of selection in island-mainland differentiation, yet the lack of congruence in the location of these regions indicates that each species evolved differently in insular environments. Our results suggest that the genomic mechanisms involved in the divergence upon island colonization-such as chromosomal inversions, and historical factors like recurrent selection-differ in each species, despite the highly conserved structure of avian genomes and the similar selective factors involved. These differences are likely influenced by factors such as genetic drift, the polygenic nature of fitness traits and the action of case-specific selective pressures.

Animals↗
PubMed1975

Isolation of arboviruses (Kemerovo group, Sakhalin group) from Ixodes uriae collected at Macquarie Island, Southern ocean.

Eighty-nine pools of ticks (Ixodes [Ceratixodes] uriae White) collected at Macquarie Island (54 degrees 30' S, 159 degrees E) in the Southern Ocean yielded 16 strains of 2 viruses, 1 a "new" member of the Kemerovo group and 1 a "new" member of the Sakhalin group. The names "Nugget" and "Taggert" are proposed for them. Antigenically-related viruses have therefore now been isolated from I. uriae in both subarctic and subantarctic regions.

Animals↗
PubMed1975

Tick-borne viruses associated with seabirds in North America and related islands.

About 18 tickborne viruses associated with seabirds are known from Canada, Mexico, the Antilles, and the United States, including its oceanic islands. Antigenic groups to which these viruses belong are Hughes, B, Sakhalin, Uukuniemi, Kemerovo, Nyamani and Quaranfil. Members of the last two groups are known in the Western Hemisphere only from Central Pacific Islands and may reflect intrusion of elements of the Australian Region. In the areas under discussion, antibody surveys have been minimal, but there is some indication of human exposure to agents of the Kemerovo group. Members of the Hughes, Nyamanini, and Quaranfil groups are all argasid tick viruses, largely tropical or subtropical in distribution, and associated particularly with gulls and terns (Laridae). The remainder, with the exception of Mono Lake (Kemerovo group, Chenuda Subgroup), which may be a virus of inland birds, are ixodid tick viruses associated mostly with seabirds of the polar or subpolar regions. All of these viruses are seen as acted upon by a common pattern of geographic and biotic factors that influences antigenic diversity of the virus and favors development of strong insular variants.

Animals↗
PubMed2026

Genomic epidemiology of coxsackievirus A24 variant during the 2024 acute hemorrhagic conjunctivitis outbreak in Coastal Kenya.

Several African countries experienced a surge in acute hemorrhagic conjunctivitis (AHC) cases in 2024. Investigations in Kenya, Mayotte (an Indian Ocean island) and Tanzania identified coxsackievirus A24 variant (CVA24v) as the causative agent. To date, however, limited genomic data exist to elucidate the sources, epidemiology, and evolution of CVA24v in Africa. We generated 245 CVA24v genomes from samples collected between January and September 2024 in coastal Kenya, representing the largest outbreak CVA24v genomic data set available globally. Phylogenetic analysis showed that these viruses belonged to genotype IV, falling into two major clusters that differed by 52 nucleotide and five amino acid changes, and with an inter-species recombination event involving another enterovirus in the 3Dpol gene. Notably, the Kenyan sequences clustered closely with contemporaneous Africa (2024) sequences, specifically Mayotte and Malawi, reflecting a regionally connected CVA24v outbreak, but were distinct from those sampled previously in Asia in 2023, with phylodynamic analysis revealing that the Most Recent Common Ancestor of Kenyan sequences existed between June and October 2023. In summary, this study provides the first detailed genomic analysis of CVA24v from Africa to inform future surveillance and control strategies.

Journal Article↗
PubMedDate not supplied

[1st case of eosinophilic meningitis in Reunion, probably due to Angiostrongylus].

Report of the case of a six-year-old child who presented a meningitis with 40 % eosinophils in the cerebrospinal fluid and which spontaneously regressed. These clinical data and the serologic (positive test for many nematod antigens) and epidemiological findings (presence of Angiostrongylus larvae in terrestrial gasteropod) lead to the conclusion that we were in presence of the first case of eosinophil meningitis due to Angiostrongylus cantonensis reported in the island of la Réunion.

Child↗
PubMed2025

Pleistocene island connectivity did not enhance dispersal or impact population size change in Galápagos geckos.

Patterns of biodiversity on remote archipelagos are largely shaped by intra-archipelago colonization followed by in situ diversification. Pleistocene sea-level fluctuations purportedly enhanced gene flow among terrestrial organisms by increasing connectivity during periods of lower sea level. Furthermore, changes in sea-level are hypothesized to impact population sizes as a result of fluctuations in island sizes. Here, we used genomic data to test the role of Pleistocene island connectivity on the diversification and demographics of leaf-toed geckos (Phyllodactylus) endemic to the Galápagos. Consistent with previous studies, we found that present diversity of Galápagos Phyllodactylus stems from three independent dispersal events. Contrary to the hypothesis of Pleistocene-driven diversification, we found no correspondence between lineage divergence and island connectivity. Furthermore, we found no evidence of introgression; demographic modelling indicated that all species increased rapidly in effective population size in the period 20-150 ka, and these inferred demographic expansions were largely asynchronous and apparently unassociated with species or island age. Collectively, these results indicate that more complex abiotic and/or biotic factors may better explain the recent demographic history of Phyllodactylus and underscore the need for additional population genomic studies of terrestrial taxa to understand the impact of past climate cycles on Galápagos island communities.

Animals↗
PubMed1979

A population study in the Maldive islands.

The Maldive Islands harbour, among 2,000 widely scattered coral islands, 190 atolls at present inhabited by over 128,000 persons. Between 1956-1976 the Royal Air Force occupied an air staging station which resulted in an increase in material and health prosperity, mostly affecting Hittadu Island. The growth rate which was 2.6% for the Maldivian population prior to that period, increased to 4.4%, resulting in a population density of 1,085 per sqkm. The unenviable prospects of the withdrawal are described.

Adolescent↗
PubMed1975

[Presence of Angiostrongylus cantonensis at la Réunion].

The eosinophilic meningitis due to Angiostrongylus cantonensis is well known on Madagascar and on Mauritius Island, but was never described on Reunion Island. Two cases have been lately oberved in Doctor Jay's department at Gabriel Martin's hospital. Local achatines were dissected and contained larvae which, when absorbed by rats, were found in there brains ten days later. These larvae belong certainly to Angiostrongylus genus, but the species has not yet been found with certitude. Lately infested rats are passing through the normal laps of time for adult maturation until they will be sacrified for further examinations.

Adult↗
PubMed1979

Bronchial asthma in the southern Maldives.

A whole population survey was performed in Addu Atoll, southern Maldives to establish the prevalence of bronchial asthma. Assessments of atopic eczema, allergic rhinitis, conjunctivitis and intestinal infection were made, and serum specific IgE titres to a number of allergens were measured. Asthma is a common condition in the southern Maldives, and there is no evidence that the IgE produced by intestinal helminths prevents the condition.

Adolescent↗
PubMed1979

Chemotherapy of falciparum malaria: regional differences in responsiveness to treatment.

A review of chloroquine and sulfa-antifol combination treated falciparum malaria patients revealed a high incidence of chloroquine-resistance, wither R1 or R2, in patients infected in Southeast Asia or Oceania. In addition, more than one tenth of the patients infected in Laos or Thailand were resistant to sulfa-antifol combinations. Chloroquine-resistant cases were sensitive to sulfa-antifol combinations. On the other hand, while all patients treated in Tokyo who had been infected in Africa or Sri Lanka were sensitive to chloroquine, a field study suggested the presence of chloroquine-resistant P. falciparum in the area near Kaduna, Nigeria. One patient infected in Nigeria showed partial resistance to the MP (sulfamonomethoxine-pyrimethamine) combination, and another patient infected in the Central African Empire showed resistance to the MP combination, increasing from R1 to R3 within a short period. The incidence of resistance to sulfa-antifol combination therapy was high in the West African tropical region. The continent, county and area of infection should be taken in consideration when selecting antimalarial drug(s) for the treatment and suppression of falciparum malaria.

Adult↗